1. Field of the Invention
Because of the polar nature of contact lenses, particularly soft contact lenses, and the environment in which soft contact lenses are handled and employed, a wide variety of materials adhere to the lenses during daily usage. During usage in the eye, the lenses are subjected to proteinaceous matter: particularly enzymes such as lysozyme; mucoproteins; and lipids, such as sterols, waxes, glycerides, phospholipids, fatty alcohols and acids. In addition to these naturally occurring materials, cosmetics, grease from the hands and dust and other materials in the air can all act together to form a strongly adhering coating to the lenses.
Soft lenses are highly porous and because of their fragile character cannot be mechanically scrubbed. In addition, the soft contact lens acts as a host for bacteria and other disease causing organisms. Many of the common bactericides are adsorbed by the soft contact lens and act as an irritant in the eye, despite careful washing of the lens after treatment with the bactericide. Therefore, one sterilization treatment involves the use of steam. The high temperature has the effect of hardening the foreign coating on the lens, particularly by denaturing proteins which may be absorbed on the lens. An accumulation of a coating can result in distortion of the lens and reduction of light transmitted through the lens.
It is therefore desirable to find a simple and efficient way to ensure the removal of strongly adhering foreign matter from soft contact lenses, as well as other contact lenses. The method should be effective over a relatively short period of time, certainly not longer than over-night, and should be safe to the user and provide a clean lens which may be readily rinsed and then be safe to be introduced into the eye.
During manufacturing of soft lenses, a blank is initially employed which is shaped to the desired prescription. During the machining of the lens, the lens accumulates various deposits, particularly oils and greases from the tools and handling. The industry has required a quick and efficient way for removing the deposits.
2. Description of the Prior Art
U.S. Pat. No. 3,689,673 teaches the use of chlorhexidene as a bactericide for sterilizing hydrophilic soft contact lenses.